Rover is a space exploration robotic vehicle used particularly in exploring the land of a planet. It has the capability to travel across the surface of a landscape and other cosmic bodies A rover has many features: It can generate power from solar panels; capture high-resolution images, move in 360 degrees with the help of a navigation camera, walk across obstacles such as bumps and rocks, conduct deep analysis and record measurements using multiple types of spectrometers, find properties of materials to identify their types and their composition; search for geological clues such as water to detect any presence of life on the landing environment .
Rovers use very sophisticated algorithms and cameras as their eye. It is very expensive to develop a single rover and send it to space. Because of this, so many countries cannot afford to launch a rocket. It is difficult to control a rover from earth, signals take more than a minute to get there so robots should decide by themselves
The Advancement in the technology forces advances in several areas of technology like the space robotics. Some technologies used in the rover are.
Sample Acquisition, Analysis
Development and integration of these technologies will allow orders of magnitude increase in the effectiveness of the remote surface operation.
The mobility of a rover should be guided with the Navigational sub-system. In Rovers, wheels are used as legs. Algorithms should be used to make optimal and safer movement from one place to other. Wheels might sink in soft soil. In this case, an error should be minimized so as to make a successful journey. Wheel slippage detection and Visual Sinkage Estimation (VSE) algorithms are used to make the mobility of the rovers more effective and efficient.
In Wheel slippage detection the general approach is based on observing many different sensor modalities implemented on the vehicle and defining deterministic conditions for wheel slippage. The output of a WS indicator can be a binary flag that indicates that WS has occurred.
Visual Sinkage Estimation (VSE) algorithm is based on an edge detection strategy which allows computational simplicity providing fast and accurate real time measurements. The methods here proposed can lead to an accurate and efficient understanding of dynamic ill-effects. Such techniques could enhance vehicle safety and mobility, through integration with control and motion planning methods
It takes a longer time to send a signal from rovers to earth and vice versa, it is impractical to continuously control space rovers from earth. Therefore, some navigation autonomy on the Rover is needed. A highly autonomous rover capable of traveling safely over long distances for many days in unfamiliar weather condition without guidance from Earth is needed. There are two types of how Navigation work on Rovers. Namely, computer aided remote driving (CARD) and semiautonomous navigation (SAN).
With CARD, stereo pictures from the rover are sent to Earth where they are viewed by a human operator using a stereo display. The operator designates a safe path for the vehicle to follow as far ahead as can be seen. This plan is sent to the rover which executes the path by dead reckoning navigation aided by computer vision. A new stereo pair of pictures is taken from the new position and the process repeats itself. Depending on the terrain, the rover might travel 5-30 meters on each of these iterations. Assuming 2-7 command cycles from earth per day, the daily traverse would be 10-200 meters .
With SAN, The rover views the local scene and, by using automatic stereo correlation or laser ranging, computes a local topographic map. This map is matched to the portion of the global map sent from earth for purposes of position determination. The high-resolution local map is analyzed by computation on the rover to determine the safe areas over which to drive. A new plan is then computed, revising the approximate route from the Earth. Using the revised path, the rover then drives ahead of a short distance (perhaps 5-10 meters), and then the process repeats. With SAN operation, a daily journey of 700-7000 meters is feasible .
We will see how algorithms of navigation work in Rovers.
Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries. Power is essential for rovers while on a mission, without power, the rover cannot move, use its science instruments, or communicate with Earth. In space, we need a source of power for a successful mission. The best-known power source is the sun, but in deep space, the lights might not be sufficient to be used for robots. For example, mars is not close to the sun relative to the earth. So other power sources have been used.
Radioisotope power system. This power system produces a dependable flow of electricity using the heat of plutonium’s radioactive decay as its “fuel.” The power source is called a “Multi-Mission Radioisotope Thermoelectric Generator” or MMRTG for short. The MMRTG converts heat from the natural radioactive decay of plutonium into electricity. This power system charges the rover’s two primary batteries. The heat from the MMRTG is also used to keep the rover’s tools and systems at their correct operating temperatures .
Rovers need to communicate with people on Earth. They need to receive commands from Earth and send the data they collect back to Earth. Special tools are needed to do this. All spacecraft have a special antenna which can send and receive information by using radio signals. Radio signals carrying commands to the spacecraft are sent out by powerful radio dishes on Earth. These radio dishes also receive the information sent to Earth by the spacecraft. Communication systems typically rely on the development of mathematical models that describe the underlying communication channel, which describe the relationship between the transmitted and the received signals.
With todays technology, we cannot stream videos from the deep space. It is because of the length between the robots and the earth. Signals travel in the speed of light 300,000km/s, it is not still enough. Deep space is not reviled yet.
Sample Acquisition, Analysis
Researches are being undertaken to decrease wastage of time while acquiring and analyzing data. Rovers are able to take samples from the celestial body and analyze the data that they got from the samples. This technique has been in use since the first rover. Scientists are looking for minerals and other information in space exploration.
The rover must have the ability to identify promising sites which contain scientifically interesting surface samples. It then must have the ability to acquire the desired samples. This will require imaging and ranging instrumentation to provide multi-spectral data for precise sample location and a robotic system to acquire the samples. This rovers can be controlled from earth or can make their own decision. As a piece information, the Apollo mission returned with samples from the lunar surface or moon. High-speed broadband multispectral data acquisition and analysis is needed in this case to make the analysis more efficient. The rovers must be able to dig inside the surface without any fault to the system or hardware. Some Algorithms are in use for this purposes.